Cleaning process for substrate surface

Abstract

Disclosed herein is a cleaning process for a substrate surface on which a high-density film and a low-density film lower in density than the high-density film are carried in combination. According to the cleaning process, a mixed gas of anhydrous hydrogen fluoride gas and a heated inert gas is brought into contact with the substrate surface such that at least a portion of the low-density film is removed without impairing the high-density film beyond a tolerance. The substrate is, for example, a semiconductor substrate.

1 . A process for cleaning a surface of a substrate, said surface carrying thereon a high-density film and a low-density film lower in density than said high-density film in combination, which comprises bringing a mixed gas of anhydrous hydrogen fluoride gas and a heated inert gas into contact with said surface of said substrate such that at least a portion of said low-density film is removed without impairing said high-density film beyond a tolerance.  
     
     
         2 . A process according to    claim 1   , wherein said high-density film is a film necessary for said substrate and said low-density film is a film unnecessary for said substrate.  
     
     
         3 . A process according to    claim 1   , wherein said low-density film includes impurities thereon or therein, and said impurities are removed together with said low-density film.  
     
     
         4 . A process according to    claim 1   , wherein said mixed gas further comprises steam added therein.  
     
     
         5 . A process according to    claim 1   , wherein said substrate is a silicon substrate, said high-density film is a thermal oxide film, and said low-density film is a natural oxide film formed on said surface of said substrate or an oxide film formed with a chemical solution on said surface of said substrate.  
     
     
         6 . A process according to    claim 1   , wherein said substrate is a substrate for a semiconductor device.  
     
     
         7 . A process according to    claim 6   , wherein said high-density film is formed on said substrate via a substrate layer.  
     
     
         8 . A process according to    claim 1   , wherein said mixed gas is maintained at a temperature between room temperature and 200° C.  
     
     
         9 . A process according to    claim 1   , wherein said mixed gas is maintained at a temperature between room temperature and 100° C.  
     
     
         10 . A process according to    claim 1   , wherein said surface of said substrate is maintained at a temperature between 30° C. to 50° C.  
     
     
         11 . A process according to    claim 1   , wherein said mixed gas has a flow rate of from 40 to 60 L/min.  
     
     
         12 . A process according to    claim 1   , wherein a concentration of anhydrous hydrogen fluoride gas contained in said mixed gas is in a range of from 1 vol. % to 3 vol. %.  
     
     
         13 . A process according to    claim 1   , wherein a concentration of anhydrous hydrogen fluoride gas contained in said mixed gas is in a range of from 1.5 vol. % to 2 vol. %.